It is known that the microbial limit test method described in Japanese Pharmacopoeia may not work for the microbial testing of Kampo crude drug products or microbial cells in the crude drugs as test samples, because target bacteria grow poorly in an ordinary commercial culture medium due to the presence of antibacterial substances (growth inhibitors) contained in the test sample.
In this case, Japanese Pharmacopoeia specifies that the influence of the antibacterial substance must be removed by any means such as dilution, filtration, neutralization, or inactivation. When the test sample is a preparation that is completely soluble in solvent, membrane filtration or the like is applicable, but if the test sample is insoluble matter, inactivation or dilution is the only means. Accordingly, there are few alternatives other than dilution.
For example, Non-Patent Document 1 describes that crude drugs and Kampo extracts have antibacterial activity, and Non-Patent Document 2 describes that cut or powdered crude drugs have antibacterial activity. However, these documents suggest no alternative for removal of antibacterial substances other than dilution.
In the cosmetics and pharmaceutical industries, inactivation of antibacterial substances is usually carried out through the addition of lecithin and polysorbate to the culture media. Culture media containing lecithin and polysorbate (for example, SCDLP medium) are commercially available, but such culture media are expensive and often not very effective for the inactivation of Kampo crude drug products, though they are highly effective for the inactivation of paraben-based and mercury-based preservatives.
Culture media containing activated carbon as an absorbent for adsorbing growth inhibitors are commercially available as special culture media. However, such culture media are not enough to remove antibacterial substances from Kampo crude drug products, crude drugs, or antibacterial foods such as spices.
Non-Patent Document 1: Bokin Bobai Vol. 25, No. 8, pp. 467-473, 1997
Non-Patent Document 2: Bokin Bobai Vol. 31, No. 9, pp. 517-525, 2003